Method and apparatus for connecting packages onto printed circuit boards

Abstract

Methods and apparatus are disclosed for attaching the integrated circuit (IC) packages to printed circuit boards (PCBs) to form smooth solder joints. A polymer flux may be provided in the process to mount an IC package to a PCB. The polymer flux may be provided on connectors of the IC package, or provided on PCB contact pad and/or pre-solder of the PCB. When the IC package is mounted onto the PCB, the polymer flux may cover a part of the connector, and may extend to cover a surface of the molding compound on the IC package. The polymer flux may completely cover the connector as well. The polymer flux delivers a fluxing component that facilitates smooth solder joint formation as well as a polymer component that offers added device protection by encapsulating individual connectors. The polymer component may be an epoxy.

What is claimed is: 
     
       1. A device comprising:
 a first substrate having a conductive line; 
 a first contact pad over the conductive line; 
 a second substrate bonded to the first substrate, the second substrate comprising a second contact pad; 
 a conductive connector physically and electrically coupling the first contact pad and the second contact pad; 
 a molding compound encapsulating a first portion of the conductive connector, the molding compound extending along sidewalls of the conductive line; and 
 a polymer material encapsulating a second portion of the conductive connector, the first portion of the conductive connector being interposed between the first contact pad and the second portion of the conductive connector, at least a portion of a first surface of the second substrate being free of the polymer material, the first surface of the second substrate facing the molding compound. 
 
     
     
       2. The device of  claim 1 , wherein the polymer material extends completely over the molding compound. 
     
     
       3. The device of  claim 1 , wherein at least a portion of an upper surface of the molding compound being free of the polymer material. 
     
     
       4. The device of  claim 1 , wherein the polymer material completely encapsulates the conductive connector between the molding compound and the second substrate. 
     
     
       5. The device of  claim 1 , wherein the polymer material extends a first distance above an outermost surface of the molding compound and extends a second distance laterally across the outermost surface of the molding compound, the second distance being greater than the first distance. 
     
     
       6. The device of  claim 1 , wherein the polymer material has of a width from about 5 um to about 30 um and a height about from about 5 um to about 50 um. 
     
     
       7. The device of  claim 1 , wherein a cross-section of the conductive connector has a plurality of concave sections facing each lateral direction. 
     
     
       8. A device comprising:
 a first substrate having a conductive line; 
 a conductive connector over the conductive line; 
 a second substrate bonded to the first substrate, the second substrate comprising a contact pad, the contact pad being coupled to the conductive connector; 
 a molding compound encapsulating a first portion of the conductive connector, the molding compound contacting the conductive line; and 
 a polymer material extending along sidewalls of a second portion of the conductive connector, at least a portion of a first surface of the second substrate being spaced apart from the polymer material, the first surface of the second substrate facing the molding compound. 
 
     
     
       9. The device of  claim 8 , wherein the polymer material contacts the second substrate. 
     
     
       10. The device of  claim 8 , wherein sidewalls of a third portion of the conductive connector are free of the polymer material, the third portion being interposed between the second portion and the second substrate. 
     
     
       11. The device of  claim 8 , wherein an uppermost surface of the molding compound is covered with the polymer material. 
     
     
       12. The device of  claim 11 , wherein a thickness of the polymer material at a location spaced apart from the conductive connector is between about 1 um and about 3 um. 
     
     
       13. The device of  claim 8 , wherein the polymer material has of a width from about 5 um to about 30 um and a height about from about 5 um to about 50 um. 
     
     
       14. A device comprising:
 a package, the package comprising:
 a first substrate having a conductive line; 
 a first contact pad on the conductive line; 
 a conductive connector physically and electrically coupled to the first contact pad; and 
 a molding compound encapsulating a first portion of the conductive connector, a second portion of the conductive connector protruding above a topmost surface of the molding compound, the molding compound contacting the conductive line; 
 a printed circuit board (PCB) bonded to the package, the PCB comprising a second contact pad, the second contact pad being physically and electrically coupled to the second portion of the conductive connector; and 
 a polymer material extending along a sidewall of the second portion of the conductive connector, a portion of a first surface of the PCB not being in physical contact with the polymer material, the portion of the first surface of the PCB facing the first substrate. 
 
 
     
     
       15. The device of  claim 14 , wherein at least a section of the second portion of the conductive connector being free of the polymer material. 
     
     
       16. The device of  claim 14 , wherein a sidewall of the second portion of the conductive connector comprises a plurality of convex sidewalls. 
     
     
       17. The device of  claim 16 , wherein the polymer material extends along only one of the plurality of convex sidewalls. 
     
     
       18. The device of  claim 16 , wherein the polymer material extends from the molding compound to the second contact pad. 
     
     
       19. The device of  claim 14 , wherein the polymer material covers a planar section of the molding compound. 
     
     
       20. The device of  claim 19 , wherein a thickness of the polymer material over the planar section of the molding compound is between about 1 um and about 3 um.